Deposition–precipitation with Urea to prepare Au/Mg(OH)2 catalysts:Influence of the preparation conditions on metal size and load

Deposition-precipitation with Urea method to prepare Au/Mg(OH)(2) was investigated. The preparation was carried out at 80 degrees C using an aqueous solution of HAuCl4 and Urea in presence of MgO as support precursor. The pH of the solution was 9.5-10 owing to the rapid hydration of MgO to Mg(OH)(2). The influence of the preparation conditions (Urea concentration, preparation procedure, addition of magnesium citrate) on the gold load and particle size distribution was evaluated. The structural characterization of preparations was carried out by means of X-ray diffractometry and transmission electron microscopy. Among the parameters investigated, the preparation procedure, that is the control of the interaction between gold species and the support, is the main step for the deposition of the highest amount of gold (> 80% of the theoretical amount) having small size and a narrow distribution (d = 4.1 nm, sigma = +/- 1.1 nm). The synthesized catalysts were tested in the CO oxidation reaction.